A Gate-Opening Control Strategy via Nitrate–Chloride Anion Exchange for Enhanced Hydrogen Isotope Separation in Metal–Organic Frameworks

Abstract

Efficient separation of hydrogen isotopes, especially deuterium (D₂), is pivotal for advancing industries such as nuclear fusion, semiconductor processing, and metabolic imaging. Current technologies, including cryogenic distillation and Girdler sulfide processes, suffer from significant limitations in selectivity and cost-effectiveness. Herein, we introduce a novel approach utilizing an imidazolium-based Metal–Organic Framework (MOF), JCM-1, designed to enhance D₂/H₂ separation through temperature-dependent gate-opening controlled by ion exchange. By substituting NO₃⁻ ions in JCM-1(NO₃⁻) with Cl⁻ ions to form JCM-1(Cl⁻), we precisely modulate the gate-opening threshold, achieving a significant enhancement in isotope selectivity. JCM-1(NO₃⁻) exhibited a D₂/H₂ selectivity (S_D2/H2) of 14.4 at 30 K and 1 bar, while JCM-1(Cl⁻) achieved an exceptional selectivity of 27.7 at 50 K and 1 mbar. This heightened performance is attributed to the reduced pore aperture and higher gate-opening temperature resulting from the Cl⁻ exchange, which optimizes the selective adsorption of D₂. Our findings reveal that JCM-1 frameworks, with their finely tunable gate-opening properties, offer a highly efficient and adaptable platform for hydrogen isotope separation. This work not only advances the understanding of ion-exchanged MOFs but also opens new pathways for targeted applications in isotope separation and other gas separation processes.